Selective-wave transmission system



-April 22 1924. h 1,491,776

J. H. HAMMOND, JR

SELECTIVEWAVE TRANSMISSION SYSTEM Original Filed May 9, 1912 'ms 4 1701mm" Patented Apr. 22, 1924.

UNITED STATES 1,491,176 PATENT OFFICE.

JOHN HAYS HAMMOND, JRL, OF GLOUCESTER, MASSACHUSETTS.

1;SELECTIVEW AVE TRANSMISSION SYSTEM.

Original application filed May 9, 1912, Serial No. 696,113. Renewed December 19, 1919, Serial No. 346,169. .mvided and this application filed October 29, 1920. Serial No. 420,439. Renewed March 15, 1924.

T all whom it may concern:

. Be it known that I. JOHN HAYS HAM-- means of Hertzian or electro-radiant Waves,

and relates more particularly to systems wherein selectivity in transmission is secured by employing distinctive wave lengths and distinctive wave-group frequencies. In the system of this invention, I secure a still higher degree of selectivity by transmitting and receiving these waves and wave-groups at a third distinctive rate which may be obtained by means of interrupters, variations of wave amplitude or in other ways, as is hereinafter more fully set forth and described.

In the accompanying drawings Figure 1 shows, in a diagrammatic form, a transmitting station containing a high $0 frequency alternator and two interrupters having difierent frequencies.

Figure 2 shows, in diagrammatic form. a receiving station having circuits responsive to three ditterent frequencies of waves and wave groups.

Figure 3 shows, in diagrammatic form, a transmitting station having a medium-frequency alternator, a high-frequency alternator and an interrupter.

Figure at shows, in diagrammatic form, a transmitting station in which an electric arc is employed as the source of the electric oscillations.

Figure 5 shows, in diagrammatic form,

a transmitting station having a high-frequency alternator, an interrupter and a mo tor-operated coil for varying the amplitude of the electric waves. I

Figure 6 shows, in diagrammatic form, a transmitting station having a high-frequency alternator and an interrupter in one circuit and a medium-frequency alternator in another circuit, both circuits being in inductive relation to the antenna.

In Figure 1, the high-frequency alter-- nator Hsupplies energy to the, coil L through the interrupters I and I and the key K. The coil L is in inductive relation with a coil L which is connected with an antenna A, grounded at E, so that all thefiO oscillations and wave variations occurring in coil L will be impressed upon the an tenna A and radiated therefrom.

The oscillation or wave frequency of the high-frequency alternator H may be, for (15 example, 300,000 per second, corresponding to a wave length of about 1000 meters, the first interrupter I, which breaks these waves up into a primary series of groups, may have a frequency of 15.000 per second, and the second interrupter I which divides these wave groups into a second series of groups or sets, may have a frequency of 750 per second. In the case assumed, each group or set of the second series will contain 20 groups of the. first Series, and each group of the first series will contain twenty wvaves. 'lhese waves and wave groups will then be radiated all together from the antenna.

This ratio of 20 to 1 between the frequencies of the waves and wave groups is merely cited as an example, and any other suitable ratio may be employed. Nor is it essential that the ratio between thev wave frequency and the first group frequency be the same as that between the first roup frequency and the second group frequcncy,but any suitable ratios to fit a particular casemay be used. It is advisable that-the first group frequency should above the limits of audibility, so that a. station attempting to interfere would have difficulty in determin-, ing its value,'but this is not essential, except when the system in which the invention is embodied is used forradio telephony.

In Figure 2, the receiving antenna circuit B L C E, consisting of the antenna B, the coil L the variable condenser C and the ground E is tuned to the wave frequency of the'waves radiated from the transmitting station, and is coupled by means of the coils L and L with the oscillation circuit L C containing the variable condenser C The oscillation circuit L C is also in tune with the wave frequency of the transmitting station. By means of the stopping condenser D and the rectifier R, the coil L receives unidirectional current from the circuit L C these impulses having a frequency equal to that of the first series of wave groups groups of the transmitter. Thecircuit, L I

'C" I which is inductively. connected with coil L, is in resonance with this second group frequency, and when the transmitting station is in operation the current impulses corresponding to the second group fre-- quency will actuate the telephone receiver P and signals will be heard.

In Figure 3, G is an alternating currentgenerator havinga frequency of, for example, 7,500 cycles per second. The current from the generator G excites the field winding of the high-frequency alternator H and so impresses a series of amplitude variations on the current of the generator H corresponding to a frequency of 335,000. The generator H? itself has a frequency in this case of 300,000 cycles per second, and delivers its current through the interrupter I and the key K to the coil L and thence by means of the coupling coil L to the antenna A which is preferably grounded as indicated at E. If it is desired that the frequency of the series of amplitude variations should bear a ratio of 20 to 1 to the interrupter frequency, then the interrupter I should have a frequency of 750 per second. 7

In this arrangement of apparatus,rthe alternator G, by its periodic amplitude variation of the high-frequency current, produces the intermediate transmission frequency, and

thustakes the place of the interrupter I of Figure 1. In Figure 4, an arc oscillatory current generator 0 is fed from a source of direct current N N. In a shunt circuit around the are O are a condenser C, an inductance coil L :ininterrupter I, and a key K, and in another shunt circuit about the are are a condenser C and an inductance coil L If the interrupter I and thekey K are closed, then, as is well known in the art, when the parts 0, C and I) are properly adjusted, .oscillatory currents will be generated in cir- Wit 0 C L I K,'the frequency of which will be dependent upon the values of the a condenser C and coil L erated in it having a frequency of 7,500"

Let this circuit be so adjusted that the frequency of these oscillations will be 300,000 per second. In a similar 'manner the circuit, 0 0 L", may be so adjusted that oscillations will be gencycles per second, and these oscillations will therefore. produce a seriesv of' amplitude By means of the cou-.

variations in the current in. circuit, O C L I K, having a frequency of 15,000 per second. a

If the interrupter I has a frequencyof 7 50 per second,'then there willbe impressed upon the antenna A, by means of the coupling coil L electric oscillations having a frequency of 300,000 with amplitude variations of a frequency of 15,000, in groups having a frequency-of 750 per second, and these waves and wave groups will be radiated from the antenna A, which ispreferably grounded as indicated at E.

a In Figure 5, H is a high-frequency alternator supplying current to the antenna A through the interrupter I, key K and coupling coils L and L". A motor M is mechanically connected to the coil L so as to rotate it in such a way as to produce a series of periodic amplitude variations, the frequencyof which is preferably above the limit of audibility, in the currentimpressed upon the antenna A. The frequency of the amplitude variations shouldbe intermediate between the frequency of the alternator H and the frequency of the interrupter I. The antenna A is .grounded at E.

In Figure 6, the high-frequency alternator H induces oscillatory currents in the antenna A through the interrupter I, and key K and the coupling coils L and L and the alternator G}, with a frequency intermediate between the frequency of the alternator H and the'frequency of the interrupter I, and preferably-above the limits of audibility, impresses variations of amplitude upon the oscillatory currents in the antenna A by means of the coupling coils L and L. The antenna A is grounded at- E.

Inthe operation of thetransmission sys tem shown in Fi 6, the alternator H and its circuit including the interrupter I and key K causes the aerial circuit A to emit a series of waves having a frequency de-- termined by the alternator H in a series of groups having an audible group frequency determined by the interrupter I. The alternator G acts upon this series of groups of waves in the aerial circuit A E produced by the alternator H and its circuit toimpress upon the waves periodic amplitude variations having a frequency in betweenthe frequency of the alternator H and the interrupter I and preferably above audibility. The waves emitted by the aerial circuit are thus divided into a second series of groups having a frequency different from the first series of groups produced by the action of the interrupter I.

In all these examples, the absolute frequencies and the relationsbetween the frequencies may be of any values suitable for each case, and the invention is not limited to any particular frequencies, Nor is this inventionlimited to the special apparatus wave groups or variations of wave amplitude transmitted, such, for example, as those described in my application for U. 8. Letters Pgltent, Serial No. 693, 380, filed April 26th, 1 f

It is also evident that by adding one or more interrupters of different frequencies to my apparatus, or by providin other suitable means for increasing the num er of difi'erent frequencies of the wave groups, I may employ four or more different wave and wavegrou fre uencies or variations of wave amp itude in one set, and so make my system additionally selective.

Havin thus described my invention, what I e aim and desire to secure by Letters Patent is 1. A signalling system comprising a transmission circuit, a circuit operatively connected to said transmission circuit in-. cluding a source of periodic electrical im- 1 pulses of a predetermined frequency, and means for varyin said impulses. at a frequency different rom said vfirst mentioned re uency, a circuit operativel connected to sai first mentioned circuit in ependentl of said second mentioned circuit and inclu ing means for producing periodic electrical impulses havm pulses havin a frequency different. from. either of'sai first mentioned fre uencies, and means for receiving electrical'lmpulses produced in said first mentioned circuit through the operation of said other Oil'f cuits, including two elements. tuned to respond to said second and third mentioned; frefiuencies, and a device arranged to be contro ed by the conjoint-action of said elements.- v 2. A signalling system comprising a transmission circuit, a circuit operatively connected to said transmission circuit'mclu'd- I mg a source of periodic electrical impulses of a predetermined frequency, and-means, for varying said impulses at a he uen'cy different from said first mentione frequenc a circuit operatively connected to said rst mentioned circuit independentl of said second mentioned circuit and inclu ing New York and means for receiving electrical impulses produced in said first mentioned circuit through the operation of said other circuits, including two elements tuned to respond to said second and third mentioned frequencies,

and a device arranged to be controlled by the conjoint and successive action of said element's.

3. A signalling system comprising a transmissioncircuit, a circuit inductively connected to said transmission circuit including a source of periodic electrical impulses of a predetermined frequency,- and means for varying said impulses at a fre u'ency different from said first mentione v quency, a circuit inductively connected to said first mentioned circuit independentl of said second mentioned circuit and includ ing means for producingperiodic electrical, impulses havinga frequency different from either of said first mentioned-frequencies, and means for receiving electrical impulses produced in said first mentioned c1rcu1t through the operation of said other circuits,f

including two elements tuned to res ond to said second and'third mentioned die/quenmissioncircuit, a circuit inductively connected to said transmission circuit includ- '80 cies, and a device arran ed to 'be controlled" ing a source of periodic electrical impulses "of a predetermined.- frequency, and means ency v for varying saidijmpulses at a freq different, from said first mentione frequency, a circuit inductively connected to said firstwmentioned circuit independently of said second mentioned circuit and me ingmeans for producing periodic electrical impulses having a frequency intermediate between said first mentioned frequencies, and means for receiving electrical impulses produced in said first mentioned circuit through the operation of said other circuits, including two elements-tuned to respond to said second and third mentioned frequencies, and a device arranged to be controlled b the conjoint and successiveaction of'sai *ele-- ments.- I p Signed at New York, in the county of and State of New York, thismeans for producing periodic electrical im- 23 day of October, A. 13. 1920. 7 Q

' .either of. sea first mentioned frequencies,

a frequency diiferent from- 1 JoHN HAYsHAmroNuI JRJ 

